Kinetosis - Motion Sickness

Motion sickness is the picture of nausea, with or without vomiting, that occurs in some people when in motion, whether inside a car, plane, train or boat.

In this text we will explain the causes of motion sickness, its most common symptoms and how to act to prevent them.

Anatomy of the ear
Anatomy of the ear
 

Understanding a disease becomes much easier when we first understand the normal functioning of the affected organs and systems. I will spend a few lines explaining how the body stays in balance so that you can understand the motion sickness more easily.

How does the body know that it is in motion?

One of the main jobs of our brain is to interpret the external messages received by the body. To know how our body is in relation to space and whether or not we are moving, the brain needs to receive and interpret information from three different systems:
  • View
  • Inner ear
  • Proprioception

We will spend a little time explaining these three systems, because their operation is quite interesting. I will try to describe these mechanisms in a very simple way.

a) Vision


Everyone can understand why vision helps the brain interpret if we are moving, as we just have to keep our eyes open to see if we are moving or not.

But vision can play tricks on us. Who, inside a car stopped at the traffic lights, never had the feeling of the car moving backwards just because the car on the side walked a little bit forward? The sight of the next car going forward can make the brain interpret that it is us who are walking backwards, causing the driver to step on the brake instinctively. This simple example shows with vision can tell the brain that we are moving, when in fact we are standing still.

b) Proprioception


This is a meaning little known by the general population. Proprioception is the ability of the brain to recognize the spatial location of the body, its position and orientation, the force exerted by the muscles and the position of each part of the body in relation to the others, without using the vision. It is the proprioception that allows us, with closed eyes, to recognize that we have our arms raised, upside down, leaning forward, with our legs bent, etc.

It is thanks to the proprioception that we can, even blindfolded, easily touch the tip of the nose with the tip of our fingers. We do not need the vision to always know where each part of our body is.

c) Internal ear


Inside the inner ear we have an organ called the labyrinth, which is part of the vestibular apparatus, responsible for maintaining balance.

The maze is a set of semicircular arches that have liquids inside. The movement of these fluids is interpreted by the brain helping to identify movements and keep us in balance.

The information passed through the labyrinth helps the brain to interpret angular movements, linear accelerations, and gravitational forces.

Labyrinthitis, which is the inflammation of this region of the inner ear, is one of the most common causes of dizziness and nausea, precisely by attacking the organ responsible for our balance.

Just as curiosity: do you know why we get dizzy after we've done it several times? Because even though we are already standing still, the liquids inside our inner ear are still in rotational motion for a few seconds, causing the brain to interpret that we are still running. If we close our eyes, the dizziness increases even more, because with open eyes, the vision can attenuate the wrong message that the inner ear is sending to the brain.

Causes of kinetosis

Motion sickness, or motion sickness, occurs when the brain receives disconnected information from these three systems.

When we walk, we are moving intentionally and the brain manages to combine the information received from vision, proprioception and inner ear. All three work in synergism, that is, saying the same thing. In a car, ship or plane, this does not occur. We are "still" but at the same time moving. If we stop to think, the human being is the only animal that usually moves passively, without having to make an effort to move. This can cause confusion in the brain.

When we are in a car, for example, we are actually moving despite the body being stopped in relation to the car. This causes a flood of confusing signals to the brain, which at the same time receives information stating that the body is stationary and effortless (with muscles and relaxed tendons) and information saying that the body is in motion thanks to acceleration and curves.

As we look forward and see the landscape go by, the brain can still better understand the movements of the car and the fact that we are moving, so most people drive without feeling sick. If, however, you lower your head and begin to read, the vision along with proprioception will tell the brain that we are standing still, while the labyrinth, stimulated by the curves and accelerations of the car, will be sending signals of movement, which facilitates the onset of nausea and dizziness.

Likewise, when we are in an amusement park simulator, the signals that the brain receives are often confused, since we are effectively stopped, just swayed to one side and the other, while our vision is receiving a lot of information, as if we were moving at high speed, accelerating and decelerating, curving up and down.

Kinetosis therefore arises whenever the brain is having difficulty interpreting the actual state of motion of our body.

Risk factors

All people are susceptible to motion sickness; what varies is the intensity of the stimulus needed to trigger the symptoms. This is easily noticed in ship trips, when some of the passengers feel very badly, others report slight discomfort and most feel nothing.

Some personal characteristics have already been identified as being at greater risk for motion sickness. For example, women are more sensitive than men, which in some ways means that men can not have motion sickness. I'll list the most common risk factors below:
  • Women
  • Children older than 2 years
  • Pregnancy
  • Labirintite
  • Migraines
  • Anxiety

The type of movement also influences the occurrence of nausea. Contrary to popular belief, low-frequency movements are those that most induce motion sickness. Traveling lying down seems to reduce the intensity of the symptoms, while standing up seems to be worse.

On ship travel, about 40% of passengers report kinetosis, with varying degrees of intensity ranging from mild malaise to strong symptoms, with incoercible vomiting. In air travel, the incidence is lower, but still reaches 25%.

Symptoms

The most common symptoms of motion sickness include nausea, vomiting, malaise, dizziness, lightheadedness, sweating, feeling hot and belching.

The symptoms of motion sickness tend to improve over time, after repeated exposure to the triggering stimulus. On ship trips, for example, the symptoms are worse in the first 72 hours, improving over time. It is also common for the patient to improve, but to get sick again when on solid ground again.

Prevention

For those people who usually get sick of cars, planes or ships, the important thing is to try to transmit through the vision the same information of movement transmitted by the inner ear. Therefore, fix the gaze at points near the horizon and always better.

For example, when on a ship, looking at the horizon conveys more sense of movement than standing inside the room, looking at the wall. The same goes for inside a car, when sitting in the front seat and looking toward the farthest terrestrial object is better than looking into the car.

Some tips:
  • Do not read during travel, especially in cars
  • The driver always feels less sick than the passengers, probably because the brain can anticipate the movements of the car in advance. If you get bored easily, avoid being the "ride”
  • On the plane, sit at the window and watch the scenery move (when there are any)
  • Also on the plane, the seats near the wings suffer less movement
  • On the ship, avoid windowless cabins
  • Do not sit with your back to the direction the vehicle is moving
  • Avoid eating on the go
  • Avoid strong odors
  • Avoid hot spots
  • Do not smoke
  • Avoid alcoholic beverages

Kinetosis while swimming

Kinetosis can also occur in people who practice swimming in the open sea. The natural rippling of the sea, the contact of cold water with the ears, and the lack of a straight line of visual reference, as are the cases of rays or lines at the bottom of the pool, are often the causes of motion sickness while swimming.

Although rare, kinesis can also occur when swimming in swimming pools. In these cases, the cause is often a wrong technique when it comes to swimming and breathing, which causes head spin during activity.

In addition to correcting the technique, the use of wax earplugs to prevent the ingress of water also often helps in some cases.

Treatment

Some medications help to minimize the effects of these conflicting signals that cause motion sickness. These remedies work best if taken preventively, that is, before the symptoms appear. Some options include:
  • Antihistamines, like Dramin
  • Scopolamine (Buscopan)
  • Promethazine + caffeine

Some of these drugs can be administered through patches implanted behind the ear.

Among non-medicated treatments, some tips usually work well. The main ones are ginger tablets. Some bracelets that make pressure on the wrist may also help in some cases, but most patients really need to take medicine to avoid nausea.
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